The need for valves operating in industrial environments processing abrasive particulate solids, for example in the production of reduced iron ores (DRI) and coal gasification, goes back for several decades. Up to date there have been a number of proposed valve designs and combination of valves addressed to find an effective and reliable operation of pressure bin locks but as of today no one of these valves has satisfied all technical requirements needed in these fields, particularly when the temperatures of the materials handled are above 500.degree.C.
One previously proposed solution to this problem is disclosed in U.S. Pat. No. 2,733,912 to Newcomb et al. Newcomb illustrates a combination of a butterfly valve for solids stopping and a plug valve for gas sealing. This patent does not teach or suggest stopping the flow of particulate solids and gas sealing with the same blocking element, with a cooled inflatable seal, nor it is adapted for high temperature usage.
U.S. Pat. No. 1,901,961 to W. F. Grant discloses a rotary valve for controlling the flow of any fluid, such as liquids or gases, and is especially adapted for use in water ways and oil mains. The valve described by Grant comprises a pressure type sealing device made of a flexible material, which is actuated by hydraulic pressure or by pressure from other sources. The seal is inflated by pressure for sealing the valve at its closed position and the pressure is relieved before opening the valve. This patent does not teach or suggest the application of the valve for controlling particulate solids nor its application at high temperatures with flammable gases under pressure. Grant does not provide a valve structure for suitable flow of solid particles because the shape of the blocking element 13 would not cut the solids flow but would get stuck when the flow channel is full of solids. This valve was conceptualized and can be used for handling fluids only.
U.S. Pat. No. 3,799,367 to Grewer et al. describes a discharge system for a shaft-type furnace which comprises a flap-type valve for stopping flow of particulate solids. This patent however does not provide an effective seal because it relies on metallic surfaces for such sealing and these surfaces can be easily scrapped and abraded by the solid particles passing through the valve.
U.S. Pat. No. 4,130,268 to Kojima et al. shows a valve structure for powdery or granular material where a single valve member has a dual function of shutoff the flow of granular material and also shutoff gas pressure. The shutoff valve member has an arcuate shape acting against the flow of solids on the concave side of said arcuate member. The gas sealing function is done on the convex side of the arcuate member. This valve structure has the disadvantage that the sealing surface of the casing (25) is abraded as the particles are deviated from their vertical free fall by the shutoff member (22) when closing the valve. This patent is mute about handling granular solids at high temperatures being restricted to applications at ambient temperatures.
U.S. Pat. No. 4,137,935 to Snowdon describes a valve assembly for closing and sealing an inlet which is full of large granular material wherein the shutoff of solid particles and the gas seal is effected by a single dome shaped member wherein both functions are made on the convex side thereof. The gas-tight seal is made by the metallic surface of the dome shaped element and an inflatable resilient circular element. The sealing element is protected against abrasion by solid particles by its position out of the possible gravitational flow of particles. The sealing surface of the dome shaped member which could get abraded does not present a sealing problem because the resilient sealing element when inflated is pressed against the metallic surface thus providing a very effective seal. This patent does not suggest any modification of the valve structure for applications at high temperatures, above 450.degree. C. where the materials employed for construction of the sealing element would get damaged. Although some polymer materials have been found withstanding temperatures up to about 260.degree. C., there are no commercially available valves for applications above said temperature.